docs: def get_abs_url(self, rel_url):
          """
          Create an absolute url from a relative one.
  
          >>> url_formatter = URLFormatter("example.com", 80)
          >>> url_formatter.get_abs_url("kml_master.kml")
          'http://example.com:80/kml_master.kml'
          """
          rel_url = rel_url.lstrip("/")
          return "{}://{}:{}/{}".format(self.url_scheme, self.host, self.port, rel_url)